Collaborative Research: Non-equilibrium Topography and Crustal-scale Imbrication in an Arc-continent Collision, Taiwan

本项目将与台湾科学家合作，研究台湾中部山脉的变形、挖掘和景观演变，重点研究最近在高海拔地区发现的低起伏斑块，这些斑块横跨山脉的顶部，与预测的陡峭崎岖的地形形成鲜明对比，该地形被认为是造山带，已达到稳定状态。研究小组将测试这样一种观点，即这些低起伏地区是在最近岩石抬升速度短暂加速之前形成的遗迹景观的抬升残留物，以及地震层析分析的初步解释表明，抬升的加速是由地壳尺度的瓦叠作用驱动的。为了验证这些相互关联的假设，研究小组将开展三个相关的研究方向：1)地貌学和宇宙成因分析（地形的详细分析；河流阶地的详细野外测绘；主要使用10Be测定低地势地区的侵蚀率）；2)基于场和地壳尺度的运动学分析（记录露头尺度断层的空间分布、相对年龄和方向，确定主要变形机制，反演断层地震数据，获得应变椭球的形状和方向）；3)热计时学研究。这项研究的综合数据集有可能改变对活跃弧-大陆碰撞的一个典型例子的地壳变形和景观演化的理解。台湾代表了地球上最活跃的构造环境之一。该岛标志着吕宋火山弧和亚洲被动边缘之间的碰撞，几十年来，碰撞推动了地球动力学模型来解释世界各地许多山带的演变。台湾的范例是，东北-西南走向的被动边缘与南北走向的火山弧之间的倾角导致山带稳定地向南扩展，并且具有时间-空间等效性，因此山带的横截面可以视为特征演化不同阶段的时间片。此外，造山带的宽度相对恒定，这使得许多工作人员主张地形稳定状态，在这种状态下，物质的流入被侵蚀所平衡。该项目旨在研究这样一种观点，即山带被干扰稳定状态系统的偶发事件所打断。本项目由地球科学部构造计划和美国国家科学基金会国际科学与工程办公室资助。

This project, in collaboration with scientists from Taiwan, will study of the deformation, exhumation, and landscape evolution of the Central Range of Taiwan with focus on recently recognized patches of low relief at high elevations that straddle the crest of the range and stand in stark contrast to the steep and rugged topography predicted for an orogenic system considered to have reached steady-state topography. The research team will test the idea that these areas of low relief are uplifted remnants of a relict landscape that formed prior to a recent transient acceleration in rock uplift rate and that the acceleration in uplift was driven by crustal-scale imbrication as suggested by preliminary interpretations of seismic tomographic analyses. To test these linked hypotheses, the team will carry out three related lines of research: 1) geomorphology and cosmogenic analyses (detailed analysis of the topography; detailed field mapping of fluvial terraces; and determination of erosion rates for the areas of low relief primarily using 10Be); 2) field-based and crustal-scale kinematic analyses (documentation of the spatial distribution, relative age, and orientation of outcrop-scale faults and kinematics; determination of the dominant deformation mechanisms; and inversion of fault earthquake data for the shape and orientation of the strain ellipsoid); 3) thermochronometry studies. The integrated dataset from this study has the potential to transform understanding of the crustal deformation and landscape evolution of one of the type examples of an active, arc-continent collision.Taiwan represents one of the most active tectonic environments on Earth. The island marks the collision between the Luzon volcanic arc and the passive margin of Asia and for decades the collision has motivated geodynamic models to explain the evolution of many mountain belts around the world. The paradigm for Taiwan is that the obliquity between the northeast-southwest trending passive margin and the north-south trending volcanic arc has led to steady southward propagation of the mountain belt and a time-for-space equivalence so that cross sections of the belt can be treated as time slices for different stages in a characteristic evolution. Moreover, the relatively constant width of the orogen has led numerous workers to argue for a topographic steady state where the influx of material is balanced by erosion. This project aims to examine the idea that the mountain belt is punctuated by episodic events that perturb the steady state system.This project is supported by the Earth Sciences Division Tectonics Program and the NSF Office of International Science and Engineering.